1. Field of the Invention
The present invention relates to a sheet storing apparatus which stacks and stores sheets fed from an image forming apparatus or the like, and relates to improvement of a sheet bundle storing mechanism which orderly stores sheet bundles bound to be bundle-shaped on a sheet placement face having height difference.
2. Description of Related Arts
In general, there has been widely known an apparatus which performs a finishing process such as a binding process as collating and stacking sheets discharged from an image forming apparatus or the like and stores a processed sheet bundle at a downstream stack tray. In such an apparatus, image-formed sheets are collated as being temporarily stacked on a processing tray from a sheet discharging path and are stacked on the stack tray after a post-process is performed thereon by a staple unit (post-processing apparatus) arranged at the processing tray. A lifting-lowering mechanism for lifting and lowering corresponding to a stacked amount of sheet bundles is arranged at the stack tray.
Further, an aligning mechanism (a sheet end regulating stopper, a biasing aligning member, or the like) which performs positioning of a sheet fed from the sheet discharging path to a predetermined processing position is arranged at the processing tray.
For example, Japanese Patent Application Laid-Open No. 2009-035371 (Patent Document 1) discloses a post-processing apparatus including a sheet aligning mechanism and a staple unit arranged at a processing tray which is arranged at the downstream side of a sheet discharging path.
Patent Document 1 also discloses an apparatus which performs a staple binding process as collating and stacking sheets fed from the sheet discharging path on the processing tray and stores a processed sheet bundle from the processing tray to a downstream stack tray.
In the apparatus of Patent Document 1, a sheet is stopped as being abutted to a regulating stopper of the processing tray while performing switch-back conveying (reverse conveying) with a reversing roller which is arranged at a sheet discharging port of the sheet discharging path. Then, staple binding is performed at a predetermined position after biasing and aligning are performed thereon in the sheet width direction with the sheet aligning mechanism.
Subsequently, the binding-processed sheet bundle is discharged to the stack tray by a conveyer mechanism arranged at the processing tray. The stack tray is structured with a lifting-lowering tray which performs lifting and lowering corresponding to stacked sheet amount. A sheet bundle is stored as dropping on a sheet placement tray from a discharging port of the processing tray with predetermined height difference.
According to an apparatus configuration in which the processing tray is arranged with a step formed at the downstream side of the sheet discharging path and the stack tray is arranged at the downstream side of the processing tray so that a leading end of a sheet fed from the sheet discharging path is supported on the upmost sheet on the processing tray and a tailing end thereof is supported by a sheet placement face of the processing tray, it is known that the apparatus can be downsized.
Further, for example, Japanese Patent No. 3960518 (Patent Document 2) discloses a sheet discharging mechanism which lowers a supporting member to support a sheet tailing end from a high position in the vicinity of a sheet discharging port onto the upmost sheet on the tray at low speed for reliably storing the sheet on a sheet placement face in an apparatus having large height difference between the sheet discharging port and the sheet placement face.
That is, Patent Document 2 discloses a mechanism with which a tailing end of a sheet bundle dropped through the sheet discharging port is supported by a supporting member and the supporting member is lifted and lowered by drive means such as a motor along a regulating face (guide fence) which regulates the sheet tailing end with abutting.
Further, Japanese Patent Application Laid-Open 2006-044896 (Patent Document 3) discloses a drive mechanism to reciprocate a supporting member which supports a tailing end of a sheet discharged from a sheet discharging port as being arranged between the sheet discharging port and a sheet placement face of a storage tray to be movable between an operating position above the storage tray and a retracting position outside the storage tray.
Patent Document 3 discloses a mechanism with which the sheet tailing end supporting member performs collating and stacking as supporting a sheet tailing end at a middle position of dropping from the sheet discharging port onto the storage tray and the sheet bundle is dropped onto the storage tray by retracting the supporting member after staple binding is performed at a sheet corner in a state of the above.